Device for withdrawal of thermal power loss of electronic or electrical components

ABSTRACT

A device for dissipation of the thermal power loss of an electronic or electromechanical component (10) is proposed, in which an adequate cooling surface area is available. To obtain the largest possible cooling surface area at low assembly outlay, the components (1) have a heat-conducting connection with a metal-coated surface of a printed circuit board (2). The coated surface parts (5, 7) protrude as far as a connecting segment (10; 10a, 10b, 10c) of a housing (8, 9) that entirely or partially surrounds the printed circuit board (2). At least one connecting segment (10, 10a, 10b, 10c) of the housing (8, 9) is embodied in crowned fashion on its surface such, that upon fastening of the housing (8, 9) to the printed circuit board (2), a durable contact pressure between the housing (8, 9) and the printed circuit board (2) is exerted by the deformation of the crowned surface.

BACKGROUND OF THE INVENTION

The invention relates to a device for dissipation of the thermal powerloss of an electronic or electromechanical component as genericallydefined by the preamble to the main claim. Such devices, in whichindividual power components are joined to heat sinks especially providedfor them are already known. For example, the power components arepressed against the heat sinks via retention springs in order to assurean adequate contact pressure. However, this requires special retainingand cooling components and separation production steps in assembly.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide adevice for withdrawal of thermal power loss of electrical or electricalcomponents, which avoids the disadvantages of the prior art.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in the device of the above mentioned general type in which thecomponents have a heat-conducting connection with a metal-coated surfaceof a printed circuit board, and the coated surface portions protrude asfar as the inside of at least one connecting segment of a housing thatentirely or partially surrounds the printed circuit board, and that theat least one connecting segment of the housing is located facing theprinted circuit board and is embodied in crowned fashion on its surfacein such a way that a durable contact pressure is exerted between thehousing and the printed circuit board as a result of the deformation ofthe crowned surface.

When the device is designed in accordance with the present invention, itis advantageous in that, in a simple way the housing takes on thefunction of the heat sink, and the requisite contact pressure for thedissipation of the heat loss is produced in conjunction with theassembly of the housing. No special retaining elements are needed. Allthe power components present on the printed circuit board are cooled inthe manner according to the invention via the housing. When the housingis assembled, the particular contact pressure required can be producedby the choice of the type of fastening and by means of a suitableassembly process.

In addition, by means of a suitable embodiment of the copper layers inaccordance with dependent claim 4, an increase in the effective surfacearea of both the copper layers on the printed circuit board and animproved dissipation of the heat loss at the connecting segments can beattained. The soldered connection between the two surfaces can easily bemade during the solder immersion bath of the printed circuit board.

The novel features which are considered as characteristic for thepresent invention are set forth in particular in the appended claims.The invention itself, however, both as to its construction and itsmethod of operation, together with additional objects and advantagesthereof, will be best understood from the following description ofspecific embodiments when read in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, a section through a fastening of a power component on a printedcircuit board;

FIG. 2, a section through an upper housing part in the form of acovering of the printed circuit board; and

FIGS. 3 and 4, a section through a schematic, enlarged detail of aconnecting segment between the housing and the printed circuit board,before and after the assembly of the housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, a power component 1, for instance a power transistor, issecured to a printed circuit board 2. The electrical connections aremade via soldered terminals 3, and a connection for carrying the lostheat onward is assured via an integrated metal plate that is permanentlyconnected to a copper layer 5. The permanent connection can be made bysoldering or for example by adhesive bonding, using a heat-conductiveadhesive. The upper copper layer 5 is joined to a lower copper layer 7via feed-through solder tags 6.

Portions of an upper housing part 8 and a lower housing part 9 which arehat or crown shaped can be seen on the right-hand end of the printedcircuit board 2; connecting segments or flanges 10 are formed both onthe on the upper side of the printed circuit board 2 and on the lowerside of the printed circuit board 2. These connecting segments 10 areshown only schematically here; the special shaping of the surface andthe fastening devices also necessary will be described in conjunctionwith the subsequent drawing figures. Heat dissipation is effected in theexemplary embodiment of FIG. 1 from the power component 1 via the copperlayers 5 and 7 to the housing parts 8 and 9. To assure good heatdissipation to the housing, a durable contact pressure F from thehousing parts 8 and 9 onto the copper layers 5 and 7 of the printedcircuit board 2 is necessary.

In FIG. 2, a section through the upper housing part 8 is shown which,after the production of the printed circuit board 2, is secured thereto.In this view, two fastening holes 11 can be seen on the sides; theyserve by way of example to receive a screw connection. In the same way,a lower housing part (not shown here) can be attained; it can be jointlyretained by the upper housing part 8 by means of a suitableinterengagement, for example. On the sides of the housing parts 8 and 9toward the printed circuit board 2, the connecting segments 10a, 10b and10c are formed, which connecting segments have a crowned surface shape,or in other words are formed like a crown. In the unmounted state theconnecting segment 10a, for instance, has an elevation of approximately0.2 to 0.4 mm beyond the corner regions at the level of the center axis12 of the housing part 8. The connecting segments 10b and 10c hereextend at right angles to the connecting segment 10a and are embodied incrowned fashion in a comparable way.

Since the crowned embodiment of the connecting segments 10a, 10b and 10ccannot be seen in FIG. 2, which is accurately to scale, this feature isillustrated enlarged and not to scale in FIGS. 3 and 4. In FIG. 3, thehousing parts 8 and 9 are shown with the connecting segments 10a priorto assembly with the printed circuit board 2. The crowned embodiment ofthe connecting segment 10a at the level of the center axis 12 is clearlyapparent here. After assembly (FIG. 4), the connecting segment 10aclosely conforms to the surface of the printed circuit board 2; thecontact pressure, effected permanently via the fastening device, notshown here, produces forces F that assure excellent contact between theprinted circuit board 2 and the housing parts 8 and 9 for optimal heatdissipation.

What is claimed is:
 1. A device for dissipation of thermal power loss ofan electronic or electromechanical component, comprising a printedcircuit board having a metal-coated surface with coated surfaceportions; a housing having two halves surrounding said printed circuitboard, each said housing half having a hat or crown shape with anenclosure section and a flange or connection section, said coatedsurface portions being aligned with portions of said connectingsegments, said connecting segments facing said printed circuit board andhaving convex surfaces which are deformed and provide a durable contactpressure between said housing and said printed circuit board with saidhousing halves fastened to said printed circuit board.
 2. A device asdefined in claim 1, wherein said housing entirely surrounds said printedcircuit board.
 3. A device as defined in claim 1, wherein said housingpartially surrounds said printed circuit board.
 4. A device as definedin claim 1, wherein said housing is a metal part.
 5. A device as definedin claim 1, wherein each of said connecting segments has a deviationfrom a plane within a range from 0.2 mm to 0.6 mm.
 6. A device asdefined in claim 1, wherein said housing entirely surrounds said printedcircuit board on at least one side; and further comprising screwconnections which secure said housing to said printed circuit board atfour corners.
 7. A device as defined in claim 1, wherein said coatedsurface portions are provided with heat-dissipating layers arranged onboth sides of said printed circuit board and joined together viafeed-through solder tags in said printed circuit board.